Recovery of the mud substrate and its associated fauna following a dry phase in a tropical lake1

Abstract

Lake Chilwa was dry for over a year. Following heavy rains, refilling was complete within 5 months, and, after 6 weeks, benthic insect populations of up to 3,500 mg m−2 were recorded. This pioneer population, mainly larvae of Chironomus transvaalensis Kieffer, disappeared 12 weeks later leaving a scanty benthic fauna resembling that of the drying phase.Isolated populations of C. transvaalensis persisted in some peripheral sites. The disappearance of fauna followed precipitation of fine grained material derived from erosion at the advancing shoreline during filling, which lowered the resistance of the larvae to major salinity variations and subsequent seasonal events. Persistence of larvae at the periphery was associated with plant debris which seemed to counteract the effects of the change in the mud.